Illuminated keyboards or backlit keyboards used in a low light or dark environment for desktop computers, laptop computers, notebook computers or Web TV sets are known in the art. Reference can be found in U.S. Pat. Nos. 6,284,988, 6,322,229, 6,199,996, 6,554,442 and 6,179,432, and R.O.C. patent publication Nos. 509955, 465777, 535385, 438035, 570235, 468833 and 516671. They mostly have a built-in luminous sheet to emit light to enable users to recognize the striking positions of the keyboard.
The aforesaid techniques have a common feature: the lighting element and the key cap are merely interposed by a trigger element and a moving mechanism. And the key cap, trigger element and moving mechanism are made from transparent material (some of them have opaque key caps with transparent character notations). The lighting element emits light from the entire sheet. The keyboard is illuminated evenly in a backlight fashion. Such a lighting mode creates problems in use, notably:
Illuminated keyboard mostly is used in a lower light or dark environment, such as on the airplane, in the car, and the like where luminance is not sufficient. With the entire keyboard illuminated, the total luminance is too strong and affects other people nearby. It the low light environment, user's visual recognition power decreases. In the occasion where the entire sheet is illuminated evenly, it is difficult for the user to recognize the individual notation on the key cap. Even if the character notation is made from opaque material, or the key cap is made from opaque material and the character notation is formed by transparent material, the light passes through between neighboring key caps and generates light interference and makes recognition difficult. For people who are not familiar the layout of character notations, striking mistakes frequently occur and erroneous output of instruction signals takes place.